Applied Mechanics and Materials Vols. 130-134

Abstract: Nanocomposite Ni-Al2O3 thin film containing nanosized Al2O3 particles had been grown on steel substrate by ultrasonic-electrodeposited technology. The optimum technological parameters of nanocomposite Ni-Al2O3 thin films were obtained by experiments and analysis. X-ray diffraction analysis was utilized to detect the crystalline and amorphous characteristics of Ni-Al2O3 thin films. The surface morphology and metallurgical structure were analysed by high resolution transmission electron microscope, and scanning electron microscope. The test results showed that nanocomposite Ni-Al2O3 thin films prepared by proper ultrasonic-electrodeposited method consist of nanometer-sized Al2O3 particles and nickel grains. And the Al2O3 nanoparticles and Ni grains diameters in thin films are about 40nm and 80nm, respectively.

Abstract: Auto Regressive model (AR) of nanoTiN particles content in Ni-TiN composite coating was established by the method of Time Series Analysis. The trend of the nanoTiN particles content variation was forecasted with the AR model,and the prediction value and experimental test results were compared. The results show the model may forecast the nanoTiN particles content in Ni-TiN composite coating. And the average deviation is about 5.2884%. The average grain size for Ni and TiN is approximately 52.85 and 39.13 nm, respectively.

Abstract: Based on artificial neural network (ANN), prediction model of the Charpy impact toughness for automatic welding is built. The input parameters of the model consist of the chemical elements and the diameter of the welding material and the outputs is the average Charpy impact toughness. The ANNs model is established by Visual C++ based on improved back-propagation (BP) arithmetic with momentum coefficients, in which the sample data used are from automatic welding materials for X70 pipeline steel. Based on the prediction model, the influence of chemical compositions, such as C, S, P, Si, Mn, Cu, Ti and Ni on the Charpy impact toughness of welding materials are analyzed. The results show that the influence of metallic elements is significantly greater than the nonmetallic, and the contents of Mn in metallic and the C in nonmetallic have primary effect on the average Charpy impact toughness.

Abstract: Based on the integrated design of structure, multi-dimensional force sensor has severe dimension coupling interference. Besides, two-order non-linear coupling error exists generally. This paper focuses on a six-axis force sensor of strain gauge balance, and uses a P normative decoupling network to compute the decoupling matrix. Then the static non-linear decoupling parameters are solved by multi-step least square so that the morbidity in the process of computing the decoupling matrix is avoided.

Abstract: Cadmium chloride and thiourea were used as raw materials to synthesize precursor solution, and CdS thin films were prepared on glass substrates by the home-made spray pyrolysis thin-film preparation device.Affects of preparation parameters, for example, the substrate temperature and fog particle velocity on the structure of CdS thin films were emphatically studied in the paper. The results showed that the optimum conditions for preparation of CdS thin films are as follows: the substrate temperature 350 °C, the gas flow rate 4L/min, and the annealing temperature 400 °C. Under the optimum conditions and argon as the carrier gas, with a spray time of 32s, a 1.9μm thickness CdS film which had a (002) plane grain size of 32.3nm was obtained. And the transmittance of the film was above 70% at the wavelength range of from 500nm to 850nm.

Abstract: Left-handed metamaterials, of which the dielectric constant and the magnetic permeability are sim-ultaneously negative , are a kind of electromagnetism materials. This paper gives a introduction to the basic principles of left-handed materials , and expatiates on the preparation ways of this materials in microwave region ,infrared region and visible light region.

Abstract: The Al-Si eutectic alloy solidified under normal pressure was prepared by vacuum Ar-arc furnace. The alloy solidified under high pressure was prepared by hexahedral anvil equipment. The two heavily etched samples were observed by scanning electron microscope. The experiments show that the eutectic silicon phase solidified under high pressure presents curved and near parallel lamellar crystal, and there is definite spacing between the layers, which was very different from that of solidified under normal pressure. So the eutectic growth mode of Al-Si alloy solidified under high pressure was put forward, which indicate that the growth mode of Si have been changed gradually from facet to non-facet under high pressure.

Abstract: Due to its buffer property, activity, absorbability and safety, magnesium hydroxide is widely used in environmental protection, pharmaceutics, pulp and paper industry, and as flame-retardant filling in composite materials. The hydrothermal synthesis of magnesium hydroxide at low temperature (< 100°C) needs only simple equipment and is environmentally friendly and energy-saving, so the process is promising and easy for industrialization. In this study, we have investigated the effects of hexamethylenetetramine and ammonia additives on the hydrating synthesis of superfine Mg (OH)₂ particles at 70°C. Mg (OH)₂ particles formed were of platelet shape and the mean diameter was approximately 200nm. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were applied to characterize the crystal phase, size distribution and morphology of the crystal particles. Different morphologies of Mg (OH)₂ particles were formed in hexamethylenetetramine and ammonia solutions. The generation velocity of hydroxyl (OH^-) was found to play an important role in the distribution and morphology of Mg (OH)₂ particles.

Abstract: Bi-axial tensile stress was applied on a polydimethylsiloxane film and mounted on a PMMA plate surface. Then, the film’s tensile strain was fixed and the gold film was sputtered onto the surface. A wrinkle pattern was found during the release of tensile strain because of the friction effect between the PMMA plate and a polydimethylsiloxane film. A nickel stamp with a wrinkle structure fabricated using electroforming process and the polymeric wrinkle structure can be replicated successfully by electroforming and by imprinting process.

Abstract: The geometric, electronic, and magnetic properties of Ho-doped Si_n (n=1-12, 16, and 18) clusters are studied via the density functional theory with the generalized gradient approximation. The results show that the Ho atom in the most stable HoSi_n clusters always occupies the surface site. Starting from n=18, the Ho atom abruptly drops into the center of Si frame, forming the Ho-encapsulated Si cages. The stabilities of HoSi_n clusters increase with increasing size n. The Ho atom in HoSi_n clusters enhances their chemical activities. Moreover, the magnetisms of HoSi_n clusters are independent of their geometric structures, and the Si and Ho atoms are antiferromagnetic.